A missense mutation in the mitochondrial cytochrome b gene in a revisited case with histiocytoid cardiomyopathy

We describe a pathogenic mutation in the mitochondrial cytochrome b gene in a patient with a multisystem disorder presenting as histiocytoid cardiomyo pathy in whom a defect of ubiquinol cytochrome c oxidonductase of the elect ron transport chain had been documented biochemically. The mutation, a G to A transition at nucleotide 15498, results in the substitution of glycine w ith aspartic acid at amino acid position 251. The mutation, which is hetero plasmic and fulfills ail accepted criteria for pathogenicity, is likely to impair the function of the holoenzyme as deduced from its effects on the cr ystal structure of ubiquinol cytochrome c oxidoreductase. This is the first molecular defect associated with histiocytoid cardiomyopathy.